Thank goodness this is on my spare gamer, not my main computer. Anyway - the machine was Vista home premium, a 100% legit OEM copy bound to it's P5B asus mobo. Ran the brand new upgrade to Win 7 Home premium (both 32 bit unfortunately) and it installed fine, but:
After a few boots it began to hang on startup. Then it wanted to repair itself but was unable to do so.
In Frustration, I did a clean install (reformatted drive C) with vista, upgraded again to Win 7. Still no joy, it again hangs on boot after a few starts. Normally I would think my hardware was buggy because I do build my own machines and I am not an expert. But this machine was running fine for a couple of years previously, so I'm a little stumped here.
In case it helps:
e6750, Asus P5B, 4 gigs of Mushkin 800, raptor 150, 8800GT, generic PSU (but as I say known to be good as it worked perfect right up to the "upgrade" to 7.)
BTW - the clean install of Vista does work, and I could just live with that I suppose, but I really wanted to add this machine to the other three in my home LAN that are running 7 - call me picky that way.

Any ideas for me?

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I build, I game, I upgrade. I build, I game, I upgrade. I build.....

if I'm right , for install the upgrade version of Windows 7, you must have a Windows XP or Vista installed and ACTIVATED . You cannot activate an upgrade version of Windows 7 on a clean drive . But if you google it you will find a way to do so. Itís ridiculous than Microsoft do not allow to perform an update , where you just insert the original disk , or even the product key code ( for disk copy reason) of Vista to prove you own it.

if I'm right , for install the upgrade version of Windows 7, you must have a Windows XP or Vista installed and ACTIVATED . You cannot activate an upgrade version of Windows 7 on a clean drive . But if you google it you will find a way to do so. Itís ridiculous than Microsoft do not allow to perform an update , where you just insert the original disk , or even the product key code ( for disk copy reason) of Vista to prove you own it.

The reason why it's make this way it's because 7 upgrade will get few of it's component from the original windows if it can. Try removing 2GB of ram or try memory stick 1 by 1. Then try another HDD. Give us some news.

One thing is shure I have a guy who told me, than he prefer buy the integral version insted of the upgrade , especially in case he need to reformat...... I guess Microsoft know about it also.... For me it's a not a problem I buy OEm , when I want to upgrade i sell the PC and just build a new one with a new Windows. So the new owner have a legit windows , all true it's probably not transferable, hey the guy of Redmond have to make money no....